U.S. patent number 5,105,851 [Application Number 07/599,330] was granted by the patent office on 1992-04-21 for apparatus for multi-path flow regulation.
This patent grant is currently assigned to Hewlett-Packard Company. Invention is credited to Kimber D. Fogelman.
United States Patent |
5,105,851 |
Fogelman |
April 21, 1992 |
Apparatus for multi-path flow regulation
Abstract
Valve assemblies are provided which comprise a housing having a
common port and n peripheral ports, where n is an even integer
greater than or equal to 4. The valve assemblies further comprise a
valve plug contained within the housing. The valve plug comprises a
distribution channel capable of fluid communication with the common
port and at least one of the peripheral ports, and (n/2)-1
switching channels capable of fluid communication with at least two
of the peripheral ports.
Inventors: |
Fogelman; Kimber D. (Newark,
DE) |
Assignee: |
Hewlett-Packard Company (Palo
Alto, CA)
|
Family
ID: |
24399196 |
Appl.
No.: |
07/599,330 |
Filed: |
October 17, 1990 |
Current U.S.
Class: |
137/625.11;
137/625.46; 137/625.47; 73/863.72 |
Current CPC
Class: |
F16K
11/083 (20130101); F16K 11/085 (20130101); G01N
30/20 (20130101); Y10T 137/86501 (20150401); G01N
2030/202 (20130101); Y10T 137/86871 (20150401); Y10T
137/86863 (20150401); G01N 2030/201 (20130101) |
Current International
Class: |
F16K
11/02 (20060101); F16K 11/083 (20060101); F16K
11/085 (20060101); G01N 30/00 (20060101); G01N
30/20 (20060101); F16K 011/06 () |
Field of
Search: |
;137/625.11,625.46,625.47 ;73/863.72 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Michalsky; Gerald A.
Claims
What is claimed is:
1. A valve assembly for the regulation of fluid flow,
comprising:
a housing comprising a common port and n peripheral ports, wherein
n is an even integer at least equal to 4; and
a valve plug positioned to rotate within the housing,
comprising:
a distribution channel capable of fluid communication with the
common port and each of the peripheral ports upon rotation of the
valve plug; and
(n/2)-1 switching channels, each switching channel capable of
simultaneous fluid communication with at least two of the
peripheral ports upon rotation of the valve plug.
2. The valve assembly of claim 1 wherein n is at least 4 and no
greater than 8.
3. The valve assembly of claim 1 wherein n is 6.
4. The valve assembly of claim 1 wherein the housing comprises an
outer face.
5. The valve assembly of claim 4 wherein the outer face comprises
at least one peripheral port.
6. The valve assembly of claim 4 wherein the outer face comprises
the common port.
7. The valve assembly of claim 1 wherein the housing comprises a
sleeve.
8. The valve assembly of claim 7 wherein the sleeve comprises at
least one peripheral port.
9. The valve assembly of claim 7 wherein the sleeve comprises the
common port.
10. The valve assembly of claim 1 wherein the housing comprises a
material selected from the group consisting of stainless steel and
polymers which are inert to the fluid.
11. The valve assembly of claim 1 wherein the housing comprises a
polymer selected from the group consisting of
poly(tetrafluoroethylene) and poly(chlorotrifluoroethylene).
12. The valve assembly of claim 1 wherein the plug comprises an end
face.
13. The valve assembly of claim 12 wherein the end face comprises
the distribution channel.
14. The valve assembly of claim 12 wherein the end face comprises
at least one switching channel.
15. The valve assembly of claim 1 wherein the plug comprises a body
having a lateral face.
16. The valve assembly of claim 15 wherein the lateral face
comprises the distribution channel.
17. The valve assembly of claim 15 wherein the lateral face
comprises at least one switching channel.
18. The valve assembly of claim 1 wherein the plug comprises a
polymer which is inert to the fluid.
19. The valve assembly of claim 1 wherein the plug comprises a
polymer selected from the group consisting of
poly(tetrafluoroethylene) and poly(chlorotrifluoroethylene).
20. The valve assembly of claim 1 wherein the plug is circular.
21. The valve assembly of claim 1 wherein the plug is conical.
22. The vale assembly of claim 1 wherein the distribution channel
and switching channels are semi-circular grooves.
23. A system for the regulation of fluid flow, comprising:
at least one terminal component;
a vale assembly in fluid communication with the terminal component,
comprising:
a housing comprising a common port and n peripheral ports, wherein
n is an even integer at least equal to 4; and
a valve plug positioned to rotate within the housing,
comprising:
a distribution channel capable of fluid communication with the
common port and each of the peripheral ports upon rotation of the
valve plug, and
(n/2)-1 switching channels, each switching channel capable of
simultaneous fluid communication with at least two of the
peripheral ports upon rotation of the valve plug; and
at least one flow-through component in fluid communication with the
valve assembly.
24. The system of claim 23 wherein the terminal component is
selected from the group consisting of fluid pumps, needles, tubing,
sorbent columns, solid phase support reins, sample loops, and waste
drains.
25. The system of claim 23 wherein the terminal component is
selected from the group consisting of fluid pumps, needles, and
waste drains.
26. The system of claim 23 wherein the flow-through component is
selected from the group consisting of tubing, sorbent columns,
solid phase support resins, and sample loops.
Description
BACKGROUND OF THE INVENTION
This invention relates to the regulation of fluid flow and, more
particularly, to the switching of fluid flow between multiple
discrete paths by means of a single valve assembly.
Instruments which rely upon regulated fluid flow are commonly
employed in a wide variety of applications, such as sample
purification, chemical analysis, clinical assay, and industrial
processing. Such instruments typically function through either
continuous or pulsed fluid flow. It will be appreciated that a
pulsed-flow instrument is any device which operates by alternately
maintaining and halting or reversing a flow stream through the
device. This may be accomplished by combinations of valves and/or
pumps to first initiate the flow and then stop or reverse it.
Very often, pulsed-flow devices require multiple flow paths to
operate efficiently. Generally, efficient operation requires
combining flow-through components, such as sorbent columns and
connective tubing, with terminal components, such as needles,
pumps, and drains. Examples of pulsed-flow devices include
laboratory water purification systems, syringe-type reagent
dispensers, manual and automated solid phase extraction (SPE)
instruments, supercritical fluid extraction (SCF) instruments,
stopped-flow spectrophotometers, automated protein or nucleic acid
sequencers and solid phase protein or nucleic acid
synthesizers.
Pulsed-flow instruments can be contrasted with continuous-flow
devices which during their normal operation require a constant,
unidirectional flow. Continuous-flow instruments also require
different flow configurations to prime the system during set up or
to perform different methods of analysis. Examples of
continuous-flow systems include high pressure liquid chromatographs
(HPLC), gas chromatographs (GC), clinical analyzers, and
flow-injection analyzers.
For both pulsed- and continuous-flow systems, at least two
different flow paths are frequently required to, for example,
isolate a component from the flow system, attach a component into
the flow system, or rearrange the order of the components in the
flow system. For many systems, three or more unique flow paths are
necessary for optimum operation.
It is known that combinations of commercially available valves can
be arranged to provide an infinite number of flow paths among the
flow-through components and terminal components employed in a flow
system. There exists the practical problem, however, of connecting
the large number of valves required for some flow path
combinations, especially when minimum volumes within the flow
system are desirable. Another problem involves properly orienting
all of the valves so as to allow the desired flow path. It will be
appreciated that as additional valves are added to the flow system,
solutions to both of these problems both more expensive and
complex.
Rotary valve assemblies having more than two flow paths are
available in a large variety of configurations. For example, radial
valve assemblies such as depicted in FIGS. 1-7 are available from
the Hamilton Corporation (Reno, Nev.). The valve assemblies
comprise a housing (10) which comprises an outer face (11) and a
sleeve (12). A common port (14) extends axially through the outer
face and a plurality of peripheral ports (13) extend radially
through the sleeve. The valve assemblies further comprise a
circular valve plug (20) contained within the housing, having a a
body (22) which has an end face (21) and a lateral face (23).
Distribution valve assemblies--such as shown in FIGS. 1 and 6--have
a circular, pore-like distribution channel (24) contained
substantially within the body. Switching valve assemblies--such as
shown in FIGS. 2 and 7--have semi-circular or square grooved
switching channels (26) on the lateral face.
Another class of radial valve assemblies, depicted in FIGS. 8-13,
are available from the Valco Corporation (Houston, Tex.). The valve
assemblies comprise a housing (50) which comprises an outer face
(51) and a sleeve (52). A common port (54) and a plurality of
peripheral ports (53) extend radially through the sleeve. The valve
assemblies further comprise a conical valve plug (60) contained
within the housing, having a body (62) which has an end face (61)
and a lateral face (63). Distribution valve assemblies--such as
shown in FIGS. 8, 11, and 12--have a semi-circular or square
grooved distribution channel (64) on the lateral face having an
axial component (64a) and a radial component (64b). Switching valve
assemblies--such as shown in FIGS. 9 and 13--have semi-circular or
square grooved switching channels (66) on the lateral face.
An axial valve assembly such as depicted in FIGS. 14-18 is
available from the Rheodyne Corporation (Cotati, Calif.). The valve
assembly comprises a housing (70) which comprises a sleeve (72) and
an outer face (71) in the form of a plate. The outer face comprises
a common port (74) and a plurality of peripheral ports (73)
extending axially through the entire thickness of the outer face.
The valve assembly further comprises a circular valve plug (80)
contained within the housing, comprising a body (88) having an end
face (86). Distribution valve assemblies comprise semi-circular
distribution channels (82) on the end face, while switching valve
assemblies comprise switching channels (84) on the end face.
Most commercially-available rotary valves are either distribution
type valves or switching (loop) type valves. Distribution valves
are characterized by having a single distribution channel which can
be turned or otherwise manipulated to connect the common port and
any one of the peripheral ports in a point-to-point configuration.
Thus, a distribution channel is capable of fluid communication with
both the common port and one of the peripheral ports. The number of
unique plug orientations for a distribution valve is determined by
the number of peripheral ports the valve assembly comprises in
addition to the common port. Peripheral ports not connected to the
common port are usually excluded from the flow system. Hence, for
each unique orientation of the valve plug only a single unique flow
path is allowed.
Switching valves are characterized by providing internal
connections between multiple, different sets of valve ports.
Switching valves have switching channels which can be manipulated
to connect two or more peripheral ports. Thus, a switching channel
is capable of fluid communication with two or more peripheral
ports. Typically, at least one terminal or flow-through component
is connected to a switching valve at two peripheral ports. Fluid
should flow from one peripheral port of the switching valve to the
component and then from the component to the other peripheral port.
As a result, components connected to switching valves have markedly
different flow path depending on the valve orientation. Generally,
switching valves contain half the number of internal channels as
they have valve ports. The channels are symmetrically arranged so
that only two unique positions of the plug are established.
However, for each unique orientation of the valve plug, multiple
flow paths through the valve may be allowed.
Combinations of distribution and switching valves are frequently
used in pulsed- and continuous-flow systems to create a large
variety of flow paths. However, multiple valve implementations
involve a large number of external connections which increases the
complexity, expense, and physical volume of the flow system. The
complexity of such systems also introduces reliability concerns.
Also, since these flow systems are typically automated, greater
reliability and lower complexity are critical for successful
instrument development.
Few examples are available in which a single valve exhibits
properties of both a switching valve and a distribution valve. One
example is the stream selection valve depicted in FIG. 19, which is
available from the Valco Corporation. The purpose of this valve is
to divert a single stream to a common outlet while maintaining flow
in all the other streams. However, this valve requires 2n+1 ports
to achieve a number, n, unique flow paths. It would be of great
advantage to provide a valve assembly having fewer ports yet
capable of providing more flow paths.
SUMMARY OF THE INVENTION
The present invention provides novel valve assemblies which
comprise a housing having a common port and n peripheral ports,
where n is an even integer greater than or equal to 4. The valve
assemblies further comprise a valve plug contained within the
housing. The valve plug comprises a distribution channel capable of
fluid communication with the common port and at least one of the
peripheral ports, and (n/2)-1 switching channels capable of fluid
communication with at least two of the peripheral ports.
The orientation of the channels on the plug is such that when the
distribution channel of the plug is aligned with one of the
peripheral ports of the housing, the switching channels each
internally connect a unique pair of peripheral ports. Further, only
n-1 peripheral ports are in communication with the distribution or
switching channels at one time; the remaining port is blocked from
the internal flow channels in the valve.
The present invention also provides systems for the regulation of
fluid flow. The systems comprise at least one terminal component, a
valve assembly according to this invention in fluid communication
with the terminal component, and at least one flow-through
component in fluid communication with the valve assembly. Different
orientations of the valve plug within the housing allow for the
isolation of terminal and/or flow-through components from the flow
system, the attachment of terminal and/or flow-through components
into the flow system, and the rearrangement of the flow-through
components in the flow system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of a radial 6-port
distribution valve assembly according to the prior art.
FIG. 2 is an exploded perspective view of a radial 6-port switching
valve assembly according to the prior art.
FIG. 3 is a bottom view of the radial valve assemblies of FIG. 1
and FIG. 2.
FIG. 4 is a cross-sectional view of the radial distribution valve
assembly of FIG. 1, taken at line X--X.
FIG. 5 is a cross-sectional view of the radial switching valve
assembly of FIG. 2, taken at line X--X.
FIG. 6 is cross-sectional view of the radial distribution valve
assembly of FIG. 1, taken at line Y--Y.
FIG. 7 is cross-sectional view of the radial switching valve
assembly of FIG. 2, taken at line Y--Y.
FIG. 8 is an exploded perspective view of a radial 6-port
distribution valve assembly according to the prior art.
FIG. 9 is an exploded perspective View of a radial 6-port switching
valve assembly according to the prior art.
FIG. 10 is a bottom view of the radial valve assemblies of FIG. 8
and FIG. 9.
FIG. 11 is a cross sectional view of the radial distribution valve
assembly of FIG. 8, taken at line X--X.
FIG. 12 is a cross-sectional view of the radial distribution valve
assembly of FIG. 8, taken at line Y--Y.
FIG. 13 is a cross-sectional view of the radial switching valve
assembly of FIG. 9, taken at line X--X.
FIG. 14 is an exploded perspective view of an axial 6-port valve
assembly according to the prior art.
FIG. 15 is a top view of the axial valve assembly of FIG. 14.
FIG. 16 is a bottom view of the axial valve assembly of FIG.
14.
FIG. 17 is a top view of the plug end face of an axial 6-port
distribution valve assembly according to the prior art.
FIG. 18 is a top view of the plug end face of an axial 6-port
switching valve assembly according to the prior art.
FIG. 19 is a diagrammatical representation of a radial stream
selection valve assembly according to the prior art.
FIG. 20 is a radial, 6-port valve assembly according to the present
invention.
FIG. 21 is a cross-sectional view of the radial valve assembly of
FIG. 20, taken at line Y--Y.
FIG. 22 is a radial, 6-port valve assembly according to the present
invention.
FIG. 23 is a cross-sectional view of the radial valve assembly of
FIG. 22, taken at line X--X.
FIG. 24 is an axial, 6-port valve assembly according to the present
invention.
FIG. 25 is a top view of the plug end face of the axial valve
assembly of FIG. 24.
FIG. 26 depicts a flow system according to the present invention,
comprising an axial 4-port valve assembly.
FIGS. 27a-27d show possible plug orientations for a flow system
corresponding to the system depicted in FIG. 26, comprising a
radial 4-port valve assembly in place of the axial 4-port valve
assembly.
FIG. 28 depicts a flow system according to the present invention,
comprising an axial 6-port valve assembly.
FIGS. 29a-29f show possible plug orientations for a flow system
corresponding to the system depicted in FIG. 28, comprising a
radial 6-port valve assembly in place of the axial 6-port valve
assembly.
FIG. 30 depicts a flow system according to the present invention,
comprising an axial 8-port valve assembly.
FIGS. 31a-31d and 32a-32d show possible plug orientations for a
flow system corresponding to the system depicted in FIG. 30,
comprising a radial 8-port valve assembly in place of the axial
8-port valve assembly.
DETAILED DESCRIPTION OF THE INVENTION
Preferred valve assemblies according to the present invention are
depicted in FIGS. 20, 22, and 24. The valve assemblies of FIGS. 20
and 24 are particularly preferred. The valve assemblies comprise a
housing (10, 50, or 70), which preferably comprises a sleeve (12,
52, or 72) attached to an outer face (11, 51, or 71). Housings can
be fabricated from a wide variety of materials. It is preferred
that housings comprise stainless steel and/or an organic polymer
which is inert to the fluids regulated by the valve. Exemplary
inert polymers are aramid polymers, acetal resins, and
poly(tetrafluoroethylene)--such as available from the DuPont
Company (Wilmington, Del.) under the tradenames Kevlar, Delrin, and
Teflon, respectively--and poly(chlorotrifluoroethylene), such as
available from the 3M Company (Newark, N.J.) under the tradename
Kel-F. Poly(tetrafluoroethylene) and poly(chlorotrifluoroethylene)
are preferred inert polymers.
The housing preferably comprises a common port (14, 54, or 74) and
peripheral ports (13, 53, or 73). It will be appreciated that a
common port is a port capable of fluid communication with each
other port of the valve assembly, depending upon the orientation of
the valve plug. Common ports preferably occupy a central location
on the housing and, in turn, on the valve assembly. Peripheral
ports are those ports other than the common port. Preferably, the
peripheral ports are equally-spaced about the common port at the
periphery of the housing. The common and peripheral ports are thus
contained in the sleeve and/or the outer face.
The housings of this invention comprise n peripheral ports, where n
is an even integer greater than or equal to 4. Preferably n is 4,
6, 8, 10, or 12. More preferably, n is 4, 6, or 8. Even more
preferred are housings wherein n is 6. Valve assemblies wherein the
housing comprises 6 peripheral ports are known as 6-port valves or
6-port valve assemblies.
Contained within the housing and in close physical contact
therewith is a circular valve plug (20, 60, or 80) having a body
(22, 62, or 88) which has an end face (21, 61, or 86) and a lateral
face (23, 63, or 87). Valve plugs can be fabricated from a wide
variety of materials. Preferred valve plugs comprise an organic
polymer which is inert to the fluids regulated by the valve, as set
forth above.
As exemplified by FIGS. 20-25, the valve plugs of this invention
comprise a distribution channel (24, 64, or 82) and (n/2)-1
switching channels (26, 66, or 84). It will be appreciated by those
skilled in the art that suitable channels for regulating fluid flow
can have a wide variety of shapes and configurations. It is
preferred that channels be configured such that there exists no
axial plane of symmetry passing through the end face of the valve
plug. It will be appreciated that such an asymmetric channel
configuration avoids flow path duplication. Preferred valve plugs
comprise circular, pore-like channels within the body of the valve
plug, semi-circular or square grooved channels on the end face or
lateral face of the valve plug, or combinations thereof. The
channels can be created by any of the mechanical and/or chemical
methods known in the art, such as etching, drilling, molding, or
stamping.
The valve assemblies of the present invention are preferably one
component in systems for the regulation of fluid flow. The flow
systems preferably comprise a terminal component in fluid
communication with the valve assembly. It will be appreciated that
a terminal component is any apparatus or device connected by
tubing, piping, or other suitable means to the valve assembly by a
single peripheral port of the valve assembly. Thus, fluid pumps,
needles, canulas, detectors, tubing, sorbent columns, solid phase
support resins, filters, sample loops, and waste drains provide
examples of terminal components.
Preferred flow systems further comprise a flow-through component.
Flow-through components include any apparatus or device connected
by tubing, piping, or other suitable means to the valve assembly by
more than one peripheral port of the valve assembly. Tubing,
sorbent columns, solid phase support resins, filters, sample loops,
detectors, sample injection valves, and valving flow systems
provide examples of flow-through components. Valve assemblies
according to the present invention preferably meet the following
criteria. They should be in a flow-allowed position when the
distribution channel of the valve plug is aligned with any of the
peripheral ports. They should contain exactly three port
connections to terminal components of the flow system. They are
preferably connected with at least one terminal component in a
manner which allows flow either into or out of a channel aligned
with the terminal component. Preferably, a terminal component is
connected to the common port of the distribution channel of the
valve. The valve assembly should also contain n-2 port connections
to flow-through components of a flow system. Each flow-through
component should be connected at two ports of the valve to provide
a flow path between these two ports. The number of flow-through
components is therefore (n/2)-1. Additionally, the two ports
connected to a flow-through component preferably are not adjacent
one another.
A flow system containing a valve assembly which meets these
criteria will have at least one configuration of components having
all of the following beneficial characteristics. Thus, the
configuration will allow n unique flow paths which each join
exactly two of the terminal components. A flow path is considered
to be the path which includes the ports, channels and flow-through
components which are in fluid communication with the two terminal
components when the valve assembly is positioned in a flow-allowed
orientation.
In such a flow system, only one flow path will be allowed for each
unique flow-allowed orientation. The path connecting the third
terminal component and any flow-through components will be
terminated at the blocked port of the valve. The component
connected to the common distribution port will be included as a
terminal component in each possible flow path.
Also, the number of flow-through components included in a given
flow path will range from zero to the maximum number of
flow-through components. Exactly two flow paths will directly
connect terminal components with no intervening flow-through
components.
Additionally, two flow paths will include all flow-through
components. The order of the flow-through components in the two
flow paths will be reversed with respect to the terminal component
connected to the common port. Further, the terminal component
connected to a peripheral port will be different in each of these
flow paths.
FIGS. 29a-29f illustrate a valve configuration for a 6-port valve
with three terminal components--the pump (102), needle (104 or -05)
and waste (106) positions--and two flow-through components--a
sample loop (108) and sorbent column (110). This valve
configuration is an example which exhibits the characteristics
stated above. FIGS. 27a-27d and FIGS. 31a-31d and 32a-32d display
4-port and 8-port valves respectively configured according to the
above rules. The set of unique flow paths for each configuration
are displayed to the right of each flow-allowed orientation of the
valve.
The advantages of the valve flow systems of the present invention
include the reduction of external connections between valves by use
of a single valve for flow path selection. External connections
undesirably increase the volume of the flow system. Another
advantage is that flow paths not connected to the distribution
channel are dead-ended to prevent uncontrolled flow.
A further advantage of the present invention is that multiple
valves need not be coordinated and monitored as with prior art
systems. This results from all paths being switched simultaneously
by a single turn of the valve plug. Also, considerable cost savings
and lowered reliability concerns are recognized by reduction of the
number of valves and actuators necessary to achieve multiple flow
paths. Fewer valves also reduces the complexity of a flow system,
which is desirable for automation of the stream selection
procedure.
Additional objects, advantages, and novel features of the present
invention will become apparent to those skilled in the art upon
examination of the following examples thereof, which are not
intended to be limiting.
EXAMPLE 1
A syringe pump is a common analytical instrument which is capable
of aspirating and dispensing fluids. Syringe pumps are therefore
useful for diluting samples, adding measured amounts of chemical
reagents, transferring bulk quantities of reagent to small
containers, or transferring fluids between two small
containers.
Accurate dispensing of small volumes of reagent requires that the
transfer line between the pump syringe and the needle, canula,
tubing end or other type of dispensing tip be filled with an
incompressible fluid. Generally, this fluid is also the reagent to
be dispensed. For expensive reagents, it is desirable to minimize
the volume of the transfer line, since any reagent remaining in
this tubing is often flushed to a waste receptacle when a new
reagent is required.
However, aspiration is commonly performed by providing a transfer
line between the pump and needle. The transfer line preferably has
sufficient volume to contain the aspirate, thus avoiding
contamination of the syringe in the pump. During aspiration, the
needle typically is lowered into the solution to be sampled and the
syringe pump is drawn back to draw the solution into the sample
loop. The aspirate may then be transferred to a second container by
replacing the original solution container with a different
container beneath the needle. A more desirable process would
transfer the sample from the loop to a container positioned beneath
a second needle. The advantage of such a process is that fewer
container movements would be necessary to effect the transfer.
Thus, a conflict occurs between the need for a minimum-volume
transfer line for dispensing and the need for large volume transfer
line for aspirating.
FIGS. 27a-27d demonstrate a 4-port flow configuration employing the
present invention. The four diagrams display the flow patterns
available at each of the four unique positions of the valve. FIGS.
27a and 27c demonstrate configurations suitable for minimum volume
dispensing to needle (104) and needle (105), respectively. FIGS.
27b and 27d demonstrate configurations suitable for aspiration.
The four flow paths of FIGS. 27a-27d provide significantly enhanced
performance of the dispenser/aspirator functions of the pump (102).
First, the paths provide for the two independent functions of
low-volume dispensing and aspiration under optimum conditions.
Second, these functions can be duplicated at two different needles
(104 and 105) which may be remote from one another. Finally, since
the two needles share the same sample loop, transfers of fluid
between the needles is possible without contamination of the
syringe. While each of these functions is individually available by
means of valve arrangements according to the prior art, no single
prior art valve configuration provides all four flow patterns in a
4-port valve.
EXAMPLE 2
An analysis of desired flow paths for a solid phase extraction
(SPE) device has been performed in which the device functions not
only as an SPE device, but also as a dispenser. Six desired flow
paths are shown in FIGS. 29a-29f.
FIG. 29a demonstrates a direct connection between the pump (102)
and the needle (104). This path would be used in dispensing small
volumes of reagent accurately, or in washing the needle.
FIG. 29b shows a path which connects the pump (102) to the needle
(104) through a sample loop (108). This path is used for aspiration
of samples from vials into the sample loop for later transfer to
either the SPE cartridge or another vial.
The path shown in FIG. 29c allows flow from the pump (102) through
the sample loop (108), through an SPE column (110), and then to the
needle (104). This path is used for applying a sample stored in the
sample loop onto the SPE column.
The path shown in FIG. 29d bypasses the sample loop (108) and flows
directly from the pump (102) through the column (110) to the needle
(104). This path solves the problem of the long lead volume between
the pump and the column. Column conditioning, washing, and elution
of the analyte would be done by this path. Also, this path
eliminates the need to load the sample only after the column is
conditioned, since sample may be stored in the sample loop while
other functions are occurring.
FIG. 29e shows a path which flows from the pump (102) to waste
(106). This path allows for changing solvents in the syringe
without having to remove vials from under the needle (104). Note
that the position referred to as "waste" could also be a needle on
a remote dispenser.
The path shown in FIG. 29f flows from the pump (102) in the reverse
direction through the column (110), through the sample loop (108),
and then to waste (106). This path allows backflushing of the
column into the sample loop. Backflushing allows the sample to be
removed from the column with a minimum amount of solvent. Setting
the path to the sample loop allows the fraction to be retained
either for delivery to a vial or to a second SPE column for
multiple column extraction methods. This permits multi-column
extractions without the need for an intermediate vial.
In analyzing the flow patterns in FIGS. 29a-29f, a pump should
always be connected to the common port to achieve the six
illustrated configurations. Also, it is desirable to prevent
uncontrolled flow to the components by closing all flow paths which
are not connected to the pump. These requirements appear to suggest
that the valve must have properties of distribution valve having at
least 6 peripheral ports. However, further examination indicates
that the flow patterns must be more than just point-to-point
connections, since four items (SPE column (110), sample loop (108).
needle (104), and waste (106)) must be connected in six different
combinations. Such connectivity is one property of a selection
valve.
Thus, the valve assembly shown in FIGS. 29a-29f is a hybrid of
prior art switching and distribution valves. This valve has six
unique flow orientations. Each orientation consists of the
distribution channel connecting the common axial port to one
peripheral port. Two pairs of peripheral ports are connected
internally by the remaining channels and the final peripheral port
is sealed against flow.
A flow system such as shown in FIGS. 29a-29f offers a number of
advantages. For example, the system achieves bidirectional positive
hydraulic displacement flow through the column bed. The column
(110) may be backflushed to elute sample in the minimum volume,
such as shown in FIGS. 29c, 29d, and 29f.
Another advantage is the provision of a direct path from pump (102)
to waste (106) for exchanging solvents within the syringe without
disturbing the rest of the flow system. This path is shown in FIG.
29e.
A further advantage is the provision of a low volume elution path
to needle (104), such as shown in FIG. 29d, wherein both flow rate
and elution volume are better controlled.
Another advantage is that the flow system provides intermediate
sample loop (108) storage of eluent. This is desireable for
multi-column cleanup. The path shown in FIG. 29f does not require
an intermediate vial, thus reducing the number of vials
required.
Also, sample loop loading, shown in FIG. 29b, need not follow
column conditioning, which is shown in FIG. 29d. That is, a column
(110) may be conditioned while sample is already in the loop
(108).
The flow system additionally has a low volume dispensing path,
shown in FIG. 29a, which reduces the amount of rinsing required.
This is desirable for expensive reagents. The high volume
aspiration path shown in FIG. 29b protects the syringe.
EXAMPLE 3
FIGS. 29a-29f demonstrate the six flow paths available to a 6-port
valve assembly according to the present invention. If the sample
loop (108) and the needle (104) in this figure are respectively
replaced by a second column and a detector, the resulting flow
system is suitable to serve as an HPLC flow system having automated
purge and column switching path selection. The choice of flow paths
provides a user the choice of configuring the system for constant
use or for switching between flow paths without disconnecting
components.
At least one of the flow paths shown in FIGS. 29a-29f also connects
directly to waste (106). This is important, since HPLC pumps
generally must be primed to flow paths with very low back pressure.
The introduction of bubbles into the pump head may require
re-priming during normal operation, which would normally require
manual disconnection of one of the components or the addition of
valves to allow this low back pressure path.
EXAMPLE 4
FIGS. 31a-31d and 32a-32d demonstrate an 8-port valve according to
the present invention. Here, three terminal components--A, E, and
F--as well as three flow-through components--B, C, and D--are
configured into the flow system. The resulting flow paths
demonstrate the variety of combinations in which the components may
be ordered in the flow system.
Those skilled in the art will appreciate that numerous changes and
modifications may be made to the preferred embodiments of the
invention and that such changes and modifications may be made
without departing from the spirit of the invention. It is therefore
intended that the appended claims cover all such equivalent
variations as fall within the true spirit and scope of the
invention.
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